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2019 Scrambler Option 719, 2013 K1600GTL,
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682 Posts
The only thing connected to the 10A circuit with the key turned off is the electronic control module. and afterwards, everything else controlled by and connected to the ecu. The key energizes the ECU and the ECU is holding the main relay closed on its own, probably through software. One minute may be how long it's programmed to stay on. I don't know. Try disconnecting the other items connected to the ECU. I'd start with the ABS module. I assume your voltmeter is reading the battery directly?
 

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2019 Scrambler Option 719, 2013 K1600GTL,
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682 Posts
I suggest you keep disconnecting stuff from the ECU. Wait. Battery voltage stays in the 12v range until you hit the starter button? It only plummets when you try to start the bike? Once you let go of the starter button, the voltage goes back up the 12v and up? What year is the bike and how many miles are on it?
 

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2019 Scrambler Option 719, 2013 K1600GTL,
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682 Posts
That's telling me that with known good batteries, and the starter is either slow to turn or not turning at all, you should get the starter checked. The other voltage drops and climbs are normal because there's a fair bit of stuff going on with the ECU and various lights. It seems the starter relay is working because the voltage is dropping significantly when you engage the starter.
 

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2019 Scrambler Option 719, 2013 K1600GTL,
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682 Posts
Got it. No attempts at starting the bike and voltage will steadily drop down as low as 10v with no intervention from you at all. The wiring diagram above shows the components controlled by the 10A fuse. The two idle actuators, the ABS module, starter relay, fuel pump and flapper valve, for a total of 6. The starter relay isn't likely the problem because it's working and you replaced the main relay. If you disconnected ALL the others, then try the handlebar connections. It seems really unlikely, but one could be stuck. You could check them with an ohm meter, or disconnect under power as the others. The only component I see that can draw heavy current is the fuel pump and you already tried it. Do you have the ability to isolate individual wires? Pulling them out of the connectors? Because now, I think you're looking for a bad handlebar switch which probably isn't drawing that kind of current, a wire rubbing metal somewhere, or the ECU itself. If you aren't sure you got the idle actuators, try disconnecting the small connector from the ECU and you'll get them both. How long from key on till volts drop below 12V?
 

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2019 Scrambler Option 719, 2013 K1600GTL,
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682 Posts
I'm starting to think the focus may be too narrow. The 10A fuse is the main power fuse so pulling it will kill power across the motorcycle, but when you have the key on, you have power going to everything but the headlight, so the whole electrical system is active.. You may want to look at the wiring for the whole bike and try disconnecting the rest of the fuses one at a time and see if you get somewhere. Do this with the key on. You can buy some more battery time by hooking up your second battery to the first, positive to positive and neg to neg. That will share the discharge between the two.
 

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2019 Scrambler Option 719, 2013 K1600GTL,
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682 Posts
All I can think of to isolate circuits would be to go to the wiring diagrams and disconnect stuff. If a wire is chafing, you can maybe find it with a thermal scanner or by looking. If you can pull pins out of connectors, disconnect the red ones.
 
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